Transcript ED Slit-Lamp Examination Andrew Shannon, MD MPH Department of Emergency Medicine

ED Slit-Lamp Examination
Andrew Shannon, MD MPH
Department of Emergency Medicine
Jacobi Medical Center
Why bother?
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ED Ophthalmology goals:
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R/O or R/I ruptured globe, retained foreign body, corneal abrasion,
diagnose HSV corneal ulcer
The Slit-lamp Exam:
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makes you look like you know what you’re doing
provides superior magnification & stabilizes pt’s head for removal of
corneal FB
tangential illumination aids in dx of uveitis/iritis
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“cells and flare”
billing?
Eye exam interactive tutorial at
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http://www.kellogg.umich.edu/theeyeshaveit/index.html
The Slit Lamp
• Low- to medium-powered binocular horizontally
mounted microscope
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Magnification
Elevation
Joystick for R/L
movement & to focus
Slit width &/or height
Slit centration or offset
Slit height & Intensity
– Slit width
• Wide- survey globe/cornea
• Narrow- depth, width & position of small abnormalities
– beam as wide as cornea is thick
– forms a parallelepiped volume: a box of illuminated tissue is seen
• Thin (slit)- narrowest beam forms an optical section
– so thin it's just discernible
– valuating small changes in clarity & pinpointing depth of pathology
– Light-source intensity
• Medium to high: most purposes
• High: optical section
– Filters
• neutral, cobalt blue (for fluorescein), red-free
– Magnification
• low power (~10x) is used for survey
• medium to high (16-40x) for optic section & parallelepiped
• high (40x) for specular reflection
– normally, light is focused at same point as microscope (“parfocal”)
“Welder’s keratitis”-- diffuse punctate lesions
of the cornea caused by UV radiation
(+) Seidel’s test: ruptured globe
dendritic appearance of HSV keratitis
linear corneal abrasion
Slit lamp technique
• Start w/ 10x eyepieces & lower powered objective
– (“1x” or “12” on JMC scopes)
• Use lowest voltage setting on transformer
– ensure open aperture
• Select the longest slit length
• Adjust chin rest
– Pt's eyes approx level w/ marker on head rest
• Slit arm in line w/ microscope
• Lamp height w/ slit beam centered vertically on Pt's
medial canthus
• Focus by moving joystick
Ocular focus to 0
adjust beam height for tall,
narrow vertical beam
locking nut: loose for free
movement
adjust width for narrow beam w/
good illumination
slit width
adjustment
magnification adjustment
beam height
slit-width adjustment
filter rheostat
slit-arm locking knob
focus
&
lamp
height
locking nut (horizontal)
intensity locking bar (vertical)
• Magnification
adjustment can be
found in various
locations, including
btwn the eyepieces
• The filter rheostat can
be used to decrease Pt
discomfort under
exam w/ the lamp
(neutral density filter)
Position of the Light
– Slit-arm pivots 1800 around microscope mount
• 450 angle, directed temporal to nasal is standard
• In-line w/ scope for initial survey of lids, lashes, lacrimals,
conjunctiva and sclera
• Methods of viewing
– Direct illumination: beam directly pointed at specimen
• gross pathology
– Retro-illumination: beam de-centered to illuminate behind
area of interest while it is still in focus
• may bring out subtle optical changes
– thin vascularization, small incisions, endothelial abnormalities
– Sclerotic scatter: light spreads by total internal reflection
• uses a beam ~1mm wide, ½ height of cornea & pointed at limbus
• subtle abnormalities as light through the cornea scatters off of any
pathology
Forehead should be in
contact w/ restraint
Eyeline should be at
level of indicator
Angle of slit-arm ~ 600
Direct/focal illumination
• Most common; focused slit; magnification 10x40x
– wide beam for surface study; narrow beam for sections
• Broad beam (parallelepiped) section of cornea
• 2mm slit: corneal surface & stroma
• to ascertain depth (FB, abrasion)
• Narrow beam (optic section): easier to determine precise depth
• resolution improved by reducing slit width; clarity improved w/ increasing mag
– angle btwn slit-arm & scope ~ 450 - 600
• increasing angle up to 900 will increase amnt of cross-section
– 4 layers of corneal section:
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tears (outer)
epithelium (& Bowman’s membrane)
stroma: seen as central gray granular area
endothelium (& Descemet’s membrane): fainter back line
– lens:
• opacities scatter & reflect more light - appear white (or pigmented) against gray
background
SLE w/ wide slit on a post-op
IOL Pt dx’d w/
Propionobacterium acnes
endophthalmitis
iris on tangential
illumination
light source
outer epithelium of cornea
SLE thru dilated pupil:
anterior chamber (AC)
SLE lateral view showing intracorneal lens anterior to native
crystalline lens
light source
cornea
crystalline lens
• van Herick’s Technique: to assess anterior chamber angle
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low mag (6x or 10x)
set beam 600 to side of scope
place narrow slit as close to limbus as possible & perpendicular to the cornea
compare width of cornea seen by optical section w/ the dark section seen btwn front
surface of iris & back of cornea
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GRADE 4: ratio of aqueous to cornea is 1:1 - open angle
GRADE 3: ratio of aqueous to cornea is 1:2 - open angle
GRADE 2: ratio of aqueous to cornea is 1:4 - narrow angle
GRADE 1: ratio is < 1:4 - dangerously narrow angle
• Conical beam: used to detect aqueous flare
– inflammatory cells in AC (eg acute anterior uveitis)
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room illumination must be completely dark
can only be seen using conical beam of light
set slit-arm angle btwn 450 -- 600
focus onto front surface of cornea w/ high magnification
– W/ pupil as dark background, flare may be seen btwn focused beam of light on
cornea & the out-of-focus beam on lens
• in normal eye this space will be clear
keratic precipitates
iris
cornea
cornea
“flare” in anterior
chamber (AC)
iris
cells & flare
cornea
no cells
or flare
cornea
iris
light source
Indirect Illumination
• Evaluate tissue outside directly illuminated area
– reduced glare; easier to view opacities, corneal nerves & limbal vessels
• focus on feature directly & then swing lamp to one side
• Retro-illumination (rarely useful in ED!)
– light reflected off deeper structures (iris or retina) w/ microscope focused on ant.
structures
• study cornea in light reflected from iris; lens in light reflected from retina
– light-opaque features are dark agnst light backgrnd (scars, pigment, vessels
containing blood)
• light-scattering features appear lighter than background (e.g. corneal precipitates)
– useful for examining size / density of opacities (not location)
– 1) use a parallelepiped beam, focus on retina
– 2) direct retro-illumination: observed corneal feature viewed in direct pathway of
reflected light
• angle btwn microscope & illuminating arm ~ 60°
– 3) indirect retro-illumination: angle is greatly reduced /increased so feature on
cornea is viewed against dark bckgrnd
keratic precipitates (direct & retro-illumination )
Hypopyon layering in AC
“Rust ring” residual from metallic FB
References:
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My Hanh Nguyen. Ophthalmology Grand Rounds. Tufts Unviersity.
http://ocw.tufts.edu/Content/37/topics/487903/488024. Content accessed 9/23/08.
Introduction to Slit Lamp Technique. CYBER-SIGHT: Copyright © 2003 Project ORBIS International Inc.
http://www.cybersight.org/bins/content_page.asp?cid=1-1581-1604. Content accessed 9/23/08.
G Papaliodis. Propionibacterium acnes Endophthalmitis. Ocular Immunology and Uveitis Foundation.
Massachusetts Eeye Research and Surgery Institution. Copyright © 1996-2008 C. Stephen Foster M.D.
http://www.uveitis.org/medical/articles/case/P_acnes.html. Content accessed 9/23/08.
Vance Thompson. Postoperative Care for Phakic Intraocular Lens Implants. In: Phakic Intraocular Lenses:
Principles and Practice by Hardten, Lindstrom, and Davis. Slack, Inc.
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Jared Schultz. One intracorneal segment treats keratoconus better than two. Copyright 2008 SLACK Inc.,
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Craig Blackwell. Narrated Eye Exam: Copyright 2008. www.blackwelleyesight.com/narrated-eye-exam/.
Content accessed 9/23/08.
Patient Glossary. Ocular Immunology and Uveitis Foundation. Massachusetts Eeye Research and Surgery
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JG O'Shea, DA Infeld, RB Harvey. Uveitis- a photoessay.
http://medweb.bham.ac.uk/easdec/eyetextbook/Uveitis/uveitis.htm. Content accessed on 9/23/08.
Second Year 99/00: Clinical Optometry 3. Slit lamp examination: Practical.
http://www.academy.org.uk/lectures/eperjesi5.htm. Content accessed 9/23/08.
KJ Knoop. Slit-lamp exam. Uptodate.com. Last updated: February 12, 2008.
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rce=search_result. Content accessed 9/23/08.